An existing snap ring is formed to have a detachable downwardly slant portion on one side of its body, through which a rope passes. This structure causes for the rope to easily escape from the snap ring due to the imperfect slant portion. In addition, the possibly escaping rope is very dangerous for people. Despite many modifications on the snap ring part where a rope is inserted, they are defective in structure so that the rope is inconveniently inserted or drawn out.